Combi-Bolter

The player nominates the initial target and rolls to hit exactly as normal. If the player makes the to hit roll he can roll one or more special sustained fire dice to see how many actual hits are scored. The first of these hits will be scored on the initial target but any extra hits can be allocated to other visible targets within 4" of the first. Once all hits have been allocated roll to wound as normal. 
The number of sustained fire dice a weapon can roll is indicated in its description in the Wargear book. A sustained fire weapon can always be fired using less dice than its maximum if desired.

Each shooting phase you can either fire just one barrel of the combi-weapon as per the normal rules or fire both barrels at the same target with a -1 to hit modifier on both shots.

Can be fired by the crew or passengers riding inside. Chaos Space Marines can rapid fire with the combi-bolters if the vehicle is stationary or moving at Slow Speed